1. Field of the Invention
The present invention relates to an iron club head for an iron golf club in which the thickness of a face of the club head is partially changed to be different.
2. Description of the Related Art
Conventionally, thicknesses of faces of club heads have been designed from the view point of strength and impact function. The thickness distribution of a club head is designed in such a way that firstly, a minimum required thickness for the face is designed which can bear an impact resulting at impact from the view point of strength, and following this, the position of center of gravity is designed, which is followed by the design of a sweet area. In designing the thickness distribution like this, the sixth sense and experience have played an important role in many cases, and in particular, in the design of the minimum required thickness, a process has been adopted in which a thickness is calculated which is required as a minimum when an impact is received at the center of the face and is then determined through verification by means of durability tests. In addition to this, when an importance is attached to the idea of low center of gravity, technical know-how depending upon the sixth sense has been made full use of to the thickness of a portion of the face lying in the vicinity of the sole is increased or to use materials of higher specific gravities in combination in the relevant portion. As club heads in which the thickness of the face surface portion is partially changed to obtain the low center of gravity and good striking feel, club heads described, for example, in JP-A-2005-279093 and JP-A-2001-29521 have been known.
However, an attempt was made in the past to design the low center of gravity in a more rational way. It was a design method of designing golf clubs with a low-toe type club head which were represented by a Browning golf club. Briefly describing, it was an idea that no face was necessary on a portion of a club head where there was no contact with a ball, and what resulted was a unique design in which a portion of a top part of the club head which lies on a toe side thereof was cut away and furthermore, the overall height of the club head was reduced. Golf clubs of this type were well supported and used by not only golfers in general but also professional golfers as a driving iron. However, golf clubs of this type disappeared from the market, because the golf industry then was too conservative to accept them and the unique design was not well accepted generally, and the trajectory became unstable in the vertical direction due to reduced inertial moment which resulted from lowering the center of gravity extremely too low.